So you've just downloaded an amazing new set of custom Photoshop Brushes. After loading the Tool Presets, you choose a Brush and start painting away on the canvas. You then make a small mistake, which of course, you want to tidy up. The Brush you were using was quite heavily textured, so to keep that texture consistent, you want to use that same Brush as an Eraser.
Well, there's actually two very simple ways of doing this:
With your Brush Tool Preset selected, go to the Options bar, and change the Mode to Clear. Instantly, your Brush will start behaving like an eraser.
Once you've finished tidying things up, simply change the Mode back to Normal.
Select the Eraser Tool (E) and right click your canvas to bring up the Brush Presets picker where you can view a history of the last seven Brushes you've used. Selecting any of these Brushes will allow you to temporarily use them as an Eraser.